1. Field of the Invention
The present invention relates generally to oil suction devices for automatic transmissions and particularly to oil suction devices for automatic transmissions that draw in oil reserved in an oil pan.
2. Description of the Background Art
Transmissions mounted on vehicles have conventionally been known.
For example Japanese Patent Laying-open No. 2000-46155 describes that a vehicular transmission including a housing having a first chamber accommodating a continuously variable transmission and a second chamber accommodating a driving-force transmission device including a starting device has an oil path in each chamber for returning lubricant oil to an oil pan.
Furthermore, Japanese Patent Laying-open No. 11-257468 describes a flat plate movable upward and downward in response to the level of the surface of oil with an oil strainer of an automatic transmission enclosed.
Furthermore, Japanese Patent Laying-open No. 11-22811 describes that an oil strainer of an automatic transmission has a suction port configured to be movable relative to the bottom of an oil pan.
When an oil pan has oil having a low liquid level reserved therein, drawing the oil into a suction port can also draws air into the suction port. For the transmission described in Japanese Patent Laying-open No. 2000-46155, the oil used for example to lubricate various devices flows from the devices downward and returns to the oil pan. However, the oil pan receives different amounts of oil at different portions for a structural ground. As such, a portion of the oil pan that receives a relatively small amount of the oil returned to the oil pan would allow air to be more readily drawn in. Such disadvantage is particularly significant at low temperatures allowing oil to increase in viscosity so that the oil pan receives reduced amounts of the oil returned thereto.
Japanese Patent Laying-open Nos. 11-257468 and 11-22811 describe that they contemplate preventing air from being drawn in as described above. However, the documents do not describe selectively preventing air from being drawn in at a portion of an oil pan that receives a small amount of the oil returned to the oil pan.